Field of the Invention
The present invention relates to a printed wiring board.
Discussion of the Background
Hitherto, in the printed wiring board constituting an electronic circuit, electronic parts are mounted on one outer layer (for example, a front surface), and the wiring pattern for providing a connection between the electronic parts is formed on the one outer layer or the other outer layer (for example, a back surface). Moreover, in the printed wiring board constituting a complicated electronic circuit, the electronic circuit is formed such that the wiring board is composed of a plurality of layers in such a way as to mount the electronic parts on the front surface and to form a wiring layer and an electric power supply layer or a ground layer (for example, an analog ground layer or a digital ground layer) on the back surface and an inner layer, for example.
The design of such printed wiring board is performed separately and independently in accordance with a function and a specification of the electronic circuit to be formed on the printed wiring board. Therefore, since a lack of commonality and versatility of the design between products is easily caused, and the applicability from one design to another design is poor, much labor and time are required for each design.
For example, a control device such as an electronic control unit (ECU) and the like to be used for a vehicle includes a small signal processing circuit configured to receive a signal from a sensor which indicates a working condition such as a rotational frequency of an engine, an opening degree of a throttle and the like for example, and to perform an amplification and the like of the signal, an arithmetic processing circuit configured to perform arithmetic processing based on the signal processed by the small signal processing circuit and to determine an control amount of load such as an actuator and the like which operates the throttle, and a driving circuit for driving the load in accordance with the determined control amount.
Then, for example, if the specifications of the engine and the performance and function (for example, existence or nonexistence of an idle stop system and the like) required therefor are different, the number and kinds of the sensors for detecting the engine condition, and/or the number and kinds of the actuators for determining the movement of the engine are varied, so that the printed wiring boards constituting the electronic control circuit are separately designed in accordance with those number and kinds accordingly.
However, the arithmetic processing circuit constituting a part of the electronic control unit, generally, includes a computer which can change the movement flexibly by software program. Therefore, when the number and kinds of the sensor signals and/or the number and kinds of the loads are varied, it is possible to deal with it by changing the executing software program of the computer, so that, essentially, the standardization, generalization or commonization of the design is easy to be performed.
Precisely, in the above-mentioned control circuit, although there is the sharable circuit part such as the arithmetic processing circuit including the computer, the whole of the printed wiring board is designed separately attributable to that one electronic circuit is formed in a state where the sharable circuit part and the circuit part to be designed separately in accordance with the specification and the like of the product to be applied are mixed.